Backyard Worlds: Planet 9

Send us your questions through the TALK network! We'll pick the most frequently asked ones and answer them here. You can also read this F.A.Q. en Español and this F.A.Q. en Français.

How to Use the Site

What are those numbers along the sides of the flipbook? The numbers alongside each image are celestial coordinates. The numbers along the bottom (The x axis) give the Right Ascension and the numbers along the left side (the y axis) are the declination. Sometimes these coordinates are called "R.A." and "dec" for short. Knowing the R.A. and dec of an object allows you to pimpoint its location on the sky. These coordinates are quite similar to longitude and latitude, which tell you the position of an object on the Earth's surface. Note, however, that while declination increases to the top of each image on this website, R.A. increases to the LEFT.

When you are discussing images on TALK, please try to use the R.A. and dec to tell other users where your favorite objects are within the image. That's how we astronomers talk, and it's also the way to look up your favorite object in other catalogs, like SIMBAD, VizieR and FinderChart (see below). For example, you might say, "Check out the light blue #mover in the bottom right corner, at R.A. 160.04, dec +29.03. It's #notinsimbad !"

Most of the time, we quote R.A. and dec in degrees: R.A. ranges from 0 to 360 degrees, and dec ranges from -90 to +90 degrees. But sometimes you'll see the R.A. and dec for a source listed as six numbers: R.A. hours, minutes and seconds and dec degrees, minutes and seconds. Here's a handy tool to convert from the hours, minutes and seconds notation to the degrees notation.

In this flipbook, there are "dipoles" everywhere! What does that mean? If you see what looks like several "dipoles" in one frame, it means there was a slight problem with the telescope pointing. The stars didn't move; the telescope did. Those are just artifacts, I'm afraid. All stellar artifacts will tend to dance around--just keep a lookout for ones that dance differently than the rest. True dipoles (slow moving objects) look like dipoles in all four images. They look a bit like black-and-white cookies, especially in the first and last frames (except that the white icing could be blue or red).

Is this a mover? It looks like a mover but only appears in two of the images. Ideally, a real mover should appear in all of the images. If an object only appears in three, it might just be a problem with random noise, so assume it really is a mover (and let the science team make the call). But if it only appears in two images, it's most likely a ghost, not a mover.

What do I do if I think I discovered something? First, be sure to mark it in every image with the marking tool. Then, make a comment on its TALK page using the #mover or #dipole hashtag with a description of where to find the object. This tells other people where to look in the image (e.g. "faint pink #dipole, upper left corner, R.A. 210.98, dec -22.53"). Next, you'll want to check to see if it has been previously published in the astronomical literature using the tools described below. If you find a mover or dipole that is not listed in SIMBAD, please fill out this form! If you don't fill out the form, we will learn about your discovery anyway from your marks with the marking tool, but it might take longer for us to get to it and research it.

I did 100 classifications! Why didn't I find anything yet? Thanks for doing all those classifications! On average it should take about 60 classifications till you spot a known high proper motion object. Of course, that's just the objects we already know about; discovering something new will take real dedication. But if you have done 100 classifications and not spotted any dipoles or movers, you might be going too fast. Take your time, stare at each of the artifacts to see if it dances around differently than the others, and make sure your the brightness of your monitor is turned all the way up. It may help to mentally divide the images into four quadrants and stare at one quadrant at a time while the animation plays. And remember, even if you don't find anything, your classifications are still useful; they are telling us about how common or rare brown dwarfs are and how to narrow down future searches for planet nine.

How Do I Use SIMBAD? SIMBAD (the Set of Identifications, Measurements, and Bibliography for Astronomical Data) is a handy database of astronomical objects used by professional astronomers and a crucial tool for us at Backyard Worlds: Planet 9. This blog post explains in detail how to use it to check whether an object you have found is already known or possibly a new discovery. Here is an abbreviated explanation.

Once you have used the numbers on the side and bottom of each image to estimate the R.A. and dec of your favorite object, you can query SIMBAD at that location to see if it lists any known astronomical objects there. For example, let's say you spotted something interesting at R.A. 277.68 degrees, dec 27.545 degrees. Go to SIMBAD's coordinate query page and type in "277.68 27.545" and hit return. Note that these coordinates are equatorial (FK4 or ICRS), not Galactic or ecliptic. We recommend setting the search radius on SIMBAD (or VizieR) to 1 arcminute. Also, if you hit the "i" in a circle on a subject's TALK page, you'll see a link to SIMBAD that will search the whole image for astronomical objects (it searches a radius of 498 arcseconds from the center of the subtile you're looking at).

If SIMBAD only finds one source on the image you're looking at, it will take you directly to a page of information about that source. Otherwise, SIMBAD will show you a list of astronomical objects listed in order of their distance from the center of the subtile. Click on the links to learn more about the objects that SIMBAD finds!

SIMBAD uses a long list of abbreviations in its tables. For example, PM* = high proper motion Star, BD* = brown dwarf, BD? = brown dwarf candidate, WD* = white dwarf. You can learn more about SIMBAD from this Users Guide.

One of the most useful features of SIMBAD is that for each object in the catalog, it pulls up a list of papers that have been written mentioning that object. Scroll down and 3/4 down the page you should see "References". You can click "sort references" and see the titles of papers where your favorite object has been mentioned or discussed, if there are any. Be sure to browse through these; your favorite object may already be the focus of a huge international debate--or it may just have played a bit part as a calibrator or an astrometric reference.

How Do I Use Finder Chart? A third check you may want to make is by looking at NASA's IRSA Finder Chart for the field. You'll find a finderchart link That will bring up many more images than what we provide on the blinking tool. Unlike the images on our website, the images on Finder Chart have not been processed to highlight time-evolving sources, however. So you may find that a field you thought was nearly empty is in fact quite crowded.

Finder Chart will show you images in several different bands: optical, infrared and mid infrared. Each one will have been taken at a different time. If your favorite object is extremely cold (like a Y dwarf or a planet), you may not see it in any other images aside from those from WISE. If the object is warm (like a star), you might see it over multiple decades from optical through mid infrared imaging. When you open Finder Chart, verify that you are looking at the same field of view that you were examining on our website by checking to see if the same stars are there. Then carefully check to see if you can identify the object in other catalogs (DSS, SDSS, 2MASS, WISE). You might want to make a note on TALK of which of these catalogs you can see it in. Also if your object is a mover, and you can see it in images from multiple catalogs (like 2MASS and WISE), see if you can see the object moving from one catalog image to the next. Make a note of the dates from each image and how many pixels (or better, arcseconds) it moved. The distance it moved divided by the difference in time (in arcseconds per year) tells you the object's tangential speed, a crucial number.

What are tiles and subtiles? The unWISE catalog divides the sky into 18,240 "tiles". We divided each of those into 64 "subtiles", which became the images you see online here. Yes, that's a lot of subtiles. The subtile number is the "ID" number that pops up when you click on the "i" in a circle under each image.

How Do I Use VizieR? If you can't find what you are looking for in SIMBAD, you can use VizieR to query a longer list of astronomical catalogs--almost every catalog that has been published! You'll find a much more thorough introduction to VizieR in this blog post. But here are a few basic tips.

First, type the R.A. and dec of your favorite object where it says "Search by Position", select a "Target dimension" of 1 arcminute and click the "Go" button. Alternatively, when you hit the "i" in a circle on a subject's TALK page, you will find a link to a VizieR query that searches within a radius of 498 arcseconds of the center of the image.

Unlike SIMBAD, VizieR gives you LOTS of source lists, one for each of the many catalogs it searches. Each list is in order of distance from location you searched (either the coordinates you estimated, or the center of the subtile). Each catalog it searches has its own special focus and caveats, so you may have to do some reading to get the most from this powerful tool. Try combing the query results for references to "proper motion" since you are most likely to have identified a moving source. E.g. you can search the page for the letters "pm" and look for objects with proper motion higher than 100 mas/yr or so. You'll often see "pmRA" for proper motion in Right Ascenscion and pmDE for proper motion in declination. If you find something that's not in VizieR, please flag it on TALK with the #notinvizier hashtag.

Note: if you do find your object on VizieR but not in SIMBAD, please submit it to the Think You've Got One form anyway.

Note: do not trust the proper motions listed in the AllWISE catalog on VizieR. They are systematically high. We're looking into the reason for this.

Why are some of the images in this flipbook black or partly black? There were a few glitches in the WISE mission that temporarily prevented it from taking data, and the result is patches of the sky where there is no data during certain epochs (i.e. time periods). For example, between April 3, 2014 and April 9, 2014, the spacecraft's computer stopped working properly, and the mission had to be put into "safe mode" while ground command reset it.

Which moving objects on here have been previously discovered? This spreadsheet lists 3036 known objects with proper motions > 600 milliarcseconds per year. You will likely run across some of them while you are searching. But even this long list doesn't cover all the possible known dipoles or movers; you will be able to see dipoles with proper motion less than 200 milliarcseconds per year. In any case be sure to check SIMBAD directly if you think you have discovered something new before reporting it using the form.

What's that giant stripe shooting across the image? It's probably a diffraction spike associated with the image of a bright star, just off the edge of the subtile you're looking at. Diffraction spikes are caused by light diffracting from the telescope's secondary mirror support structure. Diffraction spikes are the reason why people traditionally draw stars with spikes shooting from them. But in reality, stars are more or less round; the spikes are created by telescopes and sometimes by our eyes.

How big are the images I'm looking at? Each image is 256 x 256 pixels, and each pixel is 2.75 arcseconds across. So the images are 704 by 704 arcseconds, or equivalently, 11.73 by 11.73 arcminutes or 0.195 by 0.195 degrees.

What do I do if I see a "mover" that goes off the edge of the image? First, read the blog post on fast movers. Then, if you decide that this object is still interesting (i.e. it's not a cosmic ray hit or some other kind of noise), there are few things you can do. First, mark it on talk with the #mover and #outofframe tags so others can follow it up.

Next, head over to WISEVIEW and type the object's coordinates in the box in the upper left (Right Ascension and declination in decimal format). Hit return and an animated image will appear similar to the one you saw at backyardworlds.org. But unlike backyardworlds.org, WISEVIEW allows you to choose your field of view (look in the upper left of the screen), so in most cases you should be able to pick a field of view that encompasses all the images of your object. Also on the left column of WISEVIEW, you'll find a link to the nearest Zooniverse subtile and many other options. For more information about WISEVIEW, written by Dan Caselden, read this blog post.

If that doesn't work, another trick that takes more effort is to click on the information icon on a Subject's TALK page (the i in a circle on the bottom right of the flipbook), you'll see the "id numbers of nearest subtiles". Those numbers will let you look up where the adjacent subjects are that you'd like to check. To look them up, there are two big files that you will need. Go to https://github.com/marckuchner/byp9 and grab
byp9.subjectnumbers0-583679.csv and byp9.subjectnumbers583680-1167359.csv.
The first column of each file lists the subtile numbers. Those are the "Subject ID" numbers from the metadata. The second column lists the subject numbers. Those are the Subject numbers from the TALK URLs. (We had to split this lookup table into two files, one for subtile numbers 0-583679, and the other for subtile numbers 583680-1167359, otherwise the files would be too big to upload.) You can look up each of those 10 "id numbers of nearest subtiles" in the appropriate .csv file and it will tell you the Subject Numbers for the TALK URLs. Stick one of those numbers at the end of the TALK URL and you can go to that flipbook's talk page, and look for your mover. Sorry this is so complicated! We will continue trying to simplify this process.

Why are the R.A. and dec of this image messed up? unWISE data is stored using a gnomonic projection, which works very well over most of the sky. But near the north and south celestial poles, lines of constant R.A. and dec no longer correspond to straight lines on our images! So, while the axis labels are still technically correct near the poles, they just aren't that useful. This is really only a problem within about 1 degree of a pole though (i.e. for less than about 0.2% of the images). Should you be lucky enough to find an interesting object in one of these regions near a pole, you'll need to use FinderChart to estimate the object's precise R.A. and dec. Just click on the i in a circle on the talk page and click on the Finderchart link. Then hover your cursor over the location corresponding to your object. The coordinates appear on the top of the FinderChart screen. You might find it useful to click on the button that says "Lock By Click" so that when you click on an object in the image, the coordinates of that object remain displayed even when you continue to move the cursor.

How do I use AstroToolBox? Many of our volunteers are enjoying AstroToolBox, a Java tool for brown dwarf hunting developed by Frank Kiwy. AstroToolBox combines a WISEView-style image viewer with catalog search tools, spectral typing tools and a variety of other features.

How many subjects (flipbooks) are there to classify? We have more than one million subjects to classify. But most of these aren't online yet. So don't trust the completeness number on the site's landing page; that only refers to the batch of subjects that is already online.

When will we start hearing results from the project?
Our Results page contains links to publications and blog posts about our results. To get the latest updates, follow us on Twitter @backyardworlds or Facebook!

General Astronomy Questions

What is planet nine supposed to look like? If it exists, planet nine will be a fast, faint mover. The Field Guide contains a simulation of how it might look in our data. Unlike brown dwarfs, planet nine is more likely to be moving horizontally in our flipbooks. Also, unlike brown dwarfs, there could be a second copy of planet nine in the data. The two copies can be up to about 12 arcminutes apart, but both copies might show up in the same as the simulation in the Field Guide shows.

Planet nine's color depends on how much methane its atmosphere contains. According to the models of Fortney et al. 2016, if the planet has a composition similar to that of the Sun, with methane gas in its atmosphere, it will be brighter in the WISE 2 band, so it will be red in the flipbooks. That situation is more likely if planet nine is more massive than Neptune. But if the methane has frozen out of its atmosphere, which seems likely if the planet is only 10 Earth masses, the planet will be brighter in the WISE 1 band, so it will appear blue in the flipbooks. It's also possible that the planet is too small and dark to see at all in our data.

If you think you found planet nine, make a comment on its TALK page using the #planet9 hashtag with a description of where to find the object (e.g. "faint pink #mover, upper left corner, R.A. 210.98, dec -22.53"). Check to see if there is an object there that is already published in the astronomical literature using the tools described in this F.A.Q.. Then, if your planet nine candidate does not turn out to be listed in SIMBAD, please fill out this form!

What are Mira variables? Many of the brightest objects you'll see at Backyard Worlds: Planet 9 are red giants, which often pulsate. To make the images you see on this site, we subtract one epoch from another, so that makes variable stars really stand out. Anyway, if you see a huge stellar artifact like the one above, it's a probably a pulsating red giant. Mira variables are a kind of pulsating red giant. These cool, giant stars become a hundred times brighter and then dimmer again over a time span of typically about a year.

What do brown dwarfs look like? Brown dwarfs, on the other hand, are known to be brighter in the WISE 2 band (4.6 microns) than in the WISE 1 band. So they appear either red or white in our color scheme. They can be "movers" or "dipoles".

Who else is searching for planet nine? Several other groups are searching for Planet Nine. The Dark Energy Survey uses a dedicated telescope at the Cerro Tololo Inter-American Observatory. The Pan-STARRS survey uses a dedicated telescope on Mt. Haleakala in Hawaii. The Subaru telescope in Hawaii is also performing a deeper but more highly targeted search. The SkyMapper survey uses a dedicated telescope at Siding Spring Observatory in Australia; this survey was the basis for another Zooniverse project, now complete, called simply "Planet 9".. The Catalina Sky Survey is sensitive to objects in the outer solar system as faint as ~22 magnitude; you can look for Planet 9 in data from this survey with the Catalina Outer Solar System Survey citizen science project.

All of these other surveys are searching in visible wavelengths using ground-based telescopes, while we here at Backyard Worlds: Planet 9 are looking in infrared wavelengths using a telescope in space. That allows us to search the entire sky, rather than being limited to a patch of sky. Nobody knows yet whether Planet 9 will be brighter at the infrared wavelengths where we are working or at visible wavelengths where the other searches are working, so it makes sense to search in both parts of the spectrum. Read Aaron Meisner's blog post to learn more.

Could there be more planets beyond planet nine? It's possible that there are more unseen planets orbiting the Sun, in addition to planet nine. Volk and Molhotra (2017) recently suggested that a tenth planet could be responsible for causing a warp in the plane of the Kuiper Belt. This small planet would likely be too faint for us to detect here at Backyard Worlds: Planet 9. Still other planets could lurk beyond planet nine's putative orbit. But there's no particular evidence in favor of an eleventh planet yet, like the dynamical evidence that we do have for a ninth planet.

Why do we care about brown dwarfs? Brown dwarfs are the link between star formation and planet formation. They have physical characteristics which overlap with both stars and planets. By counting their numbers and determining their masses, we can learn about how stars, planets and galaxies form. Cool brown dwarfs are especially handy because we use them as analogs to exoplanets. They are the same size as Jupiter, and sometimes the same temperature as Jupiter or even Earth, yet they are far easier to study than exoplanets because do not orbit bright stars that would overwhelm them with glare. Consequently, we can get very detailed information about their atmospheres, which tells us about their composition, rotation, clouds, storms and even magnetic properties. Some brown dwarfs even have planets that orbit them. Working with you on this citizen science project, we hope to uncover exotic brown dwarfs with cloud features that will help us understand the diversity of atmospheres found in exoplanets. To learn more, read Jackie Faherty's blog post.

How many brown dwarfs do we expect to find? We have a reasonably good idea of how many stars and brown dwarfs there are nearby with spectral types of L2 and earlier (hotter), but most of these have probably been found already. The later (cooler) types remain mysterious. One of our major goals at Backyard Worlds: Planet 9 is to resolve this very question of how common the coolest brown dwarfs are!

Back in 2012, Kirkpatrick et al. 2012 estimated that there are about 5 brown dwarfs with types T6-T8.5 and at least 6 of types T9 and later (cooler) within 7 parsecs from the Sun. But then Luhman (2014) discovered a new object called WISE J085510.83-071442.5 that broke the record for coolest brown dwarf, and that forced people to re-do their estimates. Since then, Zapatero Osorio et al. 2016 estimated that there should be between 15 and 60 Y2 dwarfs closer than 7 parsecs from the Sun. Meanwhile, Yates et al. 2016 predict that within 10 parsecs of the Sun, there are about 3 Y dwarfs with types in the range Y0 to Y0.5, and only about 1 with a later (cooler) spectral type (i.e. Y1 Y2 etc.). As you can see, the wide range of these estimates arises because they are extrapolations from a list containing only a handful of objects.

How many brown dwarfs are already known? Thousands. DwarfArchives.org presently lists 1281 brown dwarfs (as of 2012). However, only twenty four known brown dwarfs are the cool (room temperature) Y dwarfs, and only three are located within 10 light years from the Sun. We hope to find more of these rare, nearby objects.

What are M dwarfs, L dwarfs, T dwarfs and Y dwarfs? Like stars, brown dwarfs are classified by the absorption lines found in their spectra, which are indicators of their surface temperatures. M dwarfs are about 3500-2100 K, L dwarfs are 2100-1300K, T dwarfs are 1300 to about 600 K, and Y dwarfs are thought to be cooler than 600 K. Since brown dwarfs are all about the same physical size, the lower the temperature, the fainter the brown dwarf. The brown dwarf "types" are a continuation of the sequence of stellar types; the full list of types goes O, B, A, F, G, K, M, L, T, Y. Each type has subtypes, indicated by numbers, which describe more subtle variations in temperature. For example, a T6 dwarf is cooler than an T3 dwarf. Both stars and brown dwarfs can be M dwarfs; brown dwarfs don't generally get hotter than about M6.

What's the closest known brown dwarf? A pair of brown dwarfs called Luhman 16 or WISE 1049-5319 is located 6.52 light years (1.99 parsecs) from the Sun; they are the closest known brown dwarfs. Maybe you will discover one that is even closer. This diagram (credit: NASA/Penn State University) shows the locations of the nearest stars and brown dwarfs.

What's the closest star to the Sun? Proxima Centauri is the closest known star to the Sun. It appears to be the faintest member of a system of three stars, called Alpha Centauri, so it is also called Alpha Centauri C. Does it seem strange that the closest known star is closer than the closest known brown dwarf? It does to us...

Can we see dwarf planets in the Kuiper Belt or other Kuiper Belt Objects in these images? No, they are too faint at these wavelengths.

What does MJD mean? MJD stands for Modified Julian Date, the number of days since midnight on November 17, 1858. Every astronomical image on this website is time stamped with a Modified Julian Date indicating when it was taken.